Head porting Tools Advice?

[hotponyshoes]

If I was making up some sort of flow bench I'd try and make something that could also be used as a dust extractor for the grinding.
Maybe a few big valves so it was easy to flick between extract/measure modes..

 

[Burdekin]

Devcon epoxy putty works fine for that even on turbo motors

Need to look into that, thanks for the tip. I was assuming this type of thing wouldn't be a starter.

 

[minimutly]

Yeah, I just meant having it calibrated at 28 inches etc. I don't know if the home made ones can do all of that.

But yeah testing valve lift flow to determine where flow stops with valve lift and gets worse would be something I would do. I'm however not chasing max hp but important not to put a cam in with too much lift.

I don't have the numbers but I think the exhaust flow would be really poor compared to the exhaust. In my head I think that is where there is a lot of power to be made matching intake and exhaust. It might be something like 65% at a guess.

There’s a reason exhaust valves and ports are smaller than intakes - they don’t need to be as big. This is because the hot exhaust gas has mucho energy, and most of it just bangs out of there. Sure, at the tail end it helps if the exhaust flows well, and that the manifold and pipes don’t prevent this (some even add to it at certain rpm), but the gains are small compared to the intake, which only has the atmosphere pushing it in (ok, plus some pressure pulse help, again at certain rpm).
If the exhaust flow is limited (and usually it will be limited by the valve for most of the time it’s off it’s seat), you could add 10 degrees of exhaust duration without losing anything usually. But really, until the intake is fully developed, And the easy wins around the seats are done, I wouldn’t be trying to hard with the exhaust port.
People have been doing this for years, there are books by people like Dave Vizard, Pete Burgess, and quite a few others, as well as some really clever software that can model the effects of adding valve area, port flow etc.
Motion Pro is one, I think I have a book which came with a disc of an early version.
Anyway, the subject is interesting, and took up years of my spare time at one point, it’s the ultimate rabbit hole, the pursuit of more power....
One thing is certain, if you build a flow bench, then you will start learning what’s what with your engine - quite a few years ago, whilst testing one of my a series heads on a Superflow bench, I came across something weird. As lntake lift went up, so did the flow, gradually decreasing. But as soon as lift got past 400 thou (or thereabouts), it started decreasing. So we tested again, same thing. Then the light came on - the valve was a Paul Ivey rimflow, waisted stem. What was happening was that the thick part of the valve was appearing out of the guide, thereby reducing flow. It was significant too. So the next head I built had 6mm valve stems...

 

[Burdekin]

There’s a reason exhaust valves and ports are smaller than intakes - they don’t need to be as big. This is because the hot exhaust gas has mucho energy, and most of it just bangs out of there. Sure, at the tail end it helps if the exhaust flows well, and that the manifold and pipes don’t prevent this (some even add to it at certain rpm), but the gains are small compared to the intake, which only has the atmosphere pushing it in (ok, plus some pressure pulse help, again at certain rpm).
If the exhaust flow is limited (and usually it will be limited by the valve for most of the time it’s off it’s seat), you could add 10 degrees of exhaust duration without losing anything usually. But really, until the intake is fully developed, And the easy wins around the seats are done, I wouldn’t be trying to hard with the exhaust port.
People have been doing this for years, there are books by people like Dave Vizard, Pete Burgess, and quite a few others, as well as some really clever software that can model the effects of adding valve area, port flow etc.
Motion Pro is one, I think I have a book which came with a disc of an early version.
Anyway, the subject is interesting, and took up years of my spare time at one point, it’s the ultimate rabbit hole, the pursuit of more power....
One thing is certain, if you build a flow bench, then you will start learning what’s what with your engine - quite a few years ago, whilst testing one of my a series heads on a Superflow bench, I came across something weird. As lntake lift went up, so did the flow, gradually decreasing. But as soon as lift got past 400 thou (or thereabouts), it started decreasing. So we tested again, same thing. Then the light came on - the valve was a Paul Ivey rimflow, waisted stem. What was happening was that the thick part of the valve was appearing out of the guide, thereby reducing flow. It was significant too. So the next head I built had 6mm valve stems...

The main supplier of modern cams these days supplies his main cam with more duration and lift on the exhaust. I think if the exhaust flows less than 75% that of the intake you are loosing power on the exhaust side. The intake has the easy wins really and not a lot can be done with the exhaust. I certainly plenty to learn, but the best flowing B20 heads have their exhaust floors raised. Don't get me wrong there's some easy wins for flow and I am only talking from what I've read. There's reasonably big restrictions directly below each valve, big guide castings, sharp short side radius (can't do anything with the exhaust due to the low floor but it is really poor and basically a 90% corner). It is a really well known head but was designed in the 50s but there are NA B20s getting over 200hp but that is not what I'm looking for, quite the opposite.

"The exhaust port stalls on the floor...it is so poorly shaped that air flowing through the port (and air ain't exhaust gas...but whatever) will shear off the short side and flow to the roof of the port."

 

[AVI_8]

Interested why a thicker head gasket would cause detonation?. Not heard of that before.

I can give you one reason why increasing the deck height could increase the chances of detonation. On engines with raised pistons designed to promote squish like the ones pictured below opening the gap slightly can cause detonation at the edge of the piston crown even though the CR has been reduced. On this particular design you want to keep the piston closer to the head

 

[PhillipM]

Squish is a massive part of combustion chamber design, screw that up with thick head gaskets and you're generally in for a bad time or at the very least have to give up serious amounts of C:R, power and low down torque/performance to get what you're wanting.

 

[optima21]

my linked post from earlier with pictures

I know some people have big budgets for their cars, and mine is pretty small, but for me its about the challenge of doing something and following my ideas, rather than having people telling me I cant do what I want to. So when I decided that I wanted to port a cylinder head for my polo, I decided that I needed to do some research instead of just attacking a cylinder head with a dremel and hoping for the best. So I ended up making a flowbench for £15 (not including the wet and dry vac I already had.

so the idea of a flowbench is to measure the the volume of air that can flow though a port at variable valve openings at a given pressure drop. Now I know it can only do that at a steady flow rather that trying to replicate the dynamics of valve opening and closing etc that happen in the real world.

so I fell across this web page

www.dwyer-inst.com/Products/AirVelocityIntroduction.cfm

and then I began to play. now I based my flowbench on 40mm plumbing fittings as they are cheap and easy to get hold of and larger than the ports I was wanting to test.

so this is my version of two nozzles needed to make a pitot tube (which measures the air velocity and because you know the diameter of the tube, you can then calculate the volume of air movement)

and here it is in a tube (shown with an early very sensitive manometer that I used but then decided that I didnt need the accuracy).

I need two manometer, a small one to measure 12" of water pressure (to measure the air velocity with the pitot tube) and a larger 36" one to measure the pressure drop between the port and atmospheric pressure. I made mine from airline for fishtanks, a peice of wood and electrical cable clips

then I needed to make a valve to adjust the pressure drop, this is like a bypass that lets the vacuum suck in unrestricted air and is opened or closed to adjust the pressure on the larger manometer. I used 25 inches of water, which is just under 1 psi.

and then there is the plate that the pumbing tubing fits to the head. yes its mdf and the centre from a roll of cellotape, but since its bore is the same as a polo engine, its all good (and cheap).

and here is the final set up show testing a head. the two manometers are in the background and plasticine is used to smooth the air flowing into the port. bolted on top of the head is a plywood plate with a threaded adjuster that opens the valve 1mm at a time.

I also made a tiny pitot tube, so I could see the differences in velocity arround the port and give an indication about what I needed to do. its a 1/16" o/d tube inside a 1/8" o/d tube.

of course its not the worlds most accurate peice of equipment, but its fit for purpose. One thing that surpised me with flow testing is the noise, as it was deafening as I needed to wear ear defenders on the standard head. of course noise is vibration which is turbulance, so and the flow gets better the noise goes as the turbulance does.

 

[optima21]

I had already decided that the ports on the polo head were too large based on articles I had read about engine tuning, and ended up developing the ports similar to the ones below (compared to standard ones at the top of the pictures). as Im too tight to buy casting silcone rubber, I used alginate which is used by dentists to take casts of teeth but is about 1/5 of the price.

the thing that suprised me was how abruptly the flow falls off on the standard port, which I think is due to ports being too large, and the changes in shape impeding the flow and creating low velocity areas which create increased turbulance (tested with the small pitot tube).

the pictures above were early tests,and the final version was similar with a higher port floor (and roof) to increase the short side radius. the port shape was developed by using plasticine in the ports and shaping that. when doing flow calculations, I kept it simple and ignored ambient air pressure and humidity, as I had a standard port I could just measure the flow in that one for comparison. I was only after an indication of what was happening to the airflow, not bothered about having xxxxxx cfm airflow and then being asked to prove it.

I went on to modify the head by reducing the ports with JB Weld, and the head is still in use 6 years later with no issues.

so the first thing to do was to roughen the inside of the ports so the JB Weld would adhere

and then to fill the edges of the ports with JB Weld, which took several days and it was done a bit at a time. show below is a port with JB weld in it and another that has been finished

and from the port throat and as you can see I didnt go for a polished finish

I ended up making my own valve seat cutters as commercial ones were far too expensive, so for the carbide cutting inserts, I used carbide electric planer blades as the were pretty cheap,and they were just glued to some slots in the cutter heads

the valves were also reprofiled,with the modified one being on the right

and the result was that when it was rolling roaded I got 98bhp at the flywheel. ( I was hoping for 100bhp, but that should be possible by tweaking the fueling and ignition).

the previous time the car was rolling roaded it had 88bhp at the flywheel (basically the same setup apart from the headwork). the engine as standard should have 75bph. and I was using standard fuel injection, standard camshaft, and standard sized pistons and valves, so I guess I didnt do too badly.

when I did this, it wasn't to see how much power I could get out of the engine, it was to improve the driveability as Im a slow driver. what has been impressive is the increase in torque across the rev range, so the engine is smoother to drive and I can trundle about at in 5th gear at 1500rpm (but dont do it too often)

 

[PhillipM]

I did similar on my old 1360cc 306 cylinder head, funnily enough with the exact same result - took it to 98bhp from the original 74 horsepower. And a nice bump in compression from optimising the squish (I took it from 9.3:1 to 10.4:1 so a hell of a jump!) made it so much more torquey low down. Damned thing used less fuel on a run too.

 

[minimutly]

Excellent first attempt, and I bet you found it useful.
Here is a gaztube vid of the PTS flowbench forum designed, homebuilt flowbench, ideal if you have a spare week and couple of hundred quid...

 

[Burdekin]

Awesome thanks guys.

 

[minimutly]

I did similar on my old 1360cc 306 cylinder head, funnily enough with the exact same result - took it to 98bhp from the original 74 horsepower. And a nice bump in compression from optimising the squish (I took it from 9.3:1 to 10.4:1 so a hell of a jump!) made it so much more torquey low down. Damned thing used less fuel on a run too.

Hmm, wet liner engine? how did you do that?

 

[PhillipM]

Skimmed the head to bring the chamber in, reduce the squish height as much as possible, then reshaped the chamber to deshroud the intake more and get it to the CC I wanted. Think I took well over 1mm off the head to get there to give me enough to play with.

 

[minimutly]

Skimmed the head to bring the chamber in, reduce the squish height as much as possible, then reshaped the chamber to deshroud the intake more and get it to the CC I wanted. Think I took well over 1mm off the head to get there to give me enough to play with.

I’m interested how you reduced the squish height?

 

[graffian]

I went though all this on some heads.
I used my nans old vacuum cleaner and assorted plastic tube I found in my dads garage.
Not having a clue what I was doing I figured I needed something to practice on, so I made
plaster models of the ports. I didn't cut any metal till I was happy with the plaster models.